Recent experimental work supported by NIA, suggests that there may be a deceleration of mortality races at the oldest ages. This deceleration has been found in four species, humans, medflies, Drosophila, and nematodes, yet the breadth of these demographic patterns is not known. The major aim of this research proposal will be to determine if mortality deceleration of the oldest-old is found in populations in nature. Biodemographic studies of aging up until now have used laboratory conditions. This will be the first study to compare the demography of a species under both natural and laboratory conditions. This project will test the genetic basis of age- specific mortality rates in order to determine whether and how much genotypes differ in their mortality trajectories and lifespans within natural populations. It will also test a major assumption of the current evolutionary theories of senescence, that the strength of selection on age- specific survival and fecundity declines with age. Because field experiments with animals are difficult, this study will use plant species in a natural environment, to determine whether senescence and mortality deceleration occur in natural populations. This is a pilot project designed to be the first step in a larger research program which will be submitted as a supplement to the NIA-funded Program Project entitled "Oldest-old mortality - Demographic models and analysis" (POl AGO876I, James Vaupel, Principal Investigator).